It has been known to measure a circuit pattern of semiconductor device actually formed on a wafer by using a design data of the circuit pattern of semiconductor device. Since the design of the circuit pattern shows an ideal shape the circuit pattern of semiconductor device has primarily, the accuracy of patterning by a semiconductor fabrication process can be evaluated by comparing the design data with a pattern actually formed on the wafer.
Recently, fineness of a semiconductor integrated circuit has been advancing and in the wake thereof, the performance of a semiconductor inspecting apparatus has been ameliorated. As one of the semiconductor inspecting apparatus as above, a CD-SEM (Critical Dimension Scanning Electron Microscope) is available. The CD-SEM is an apparatus in which the dimension of a pattern formed on a sample is measured on the basis of secondary electrons obtained by scanning an electron beam, a kind of charged-particle beam, on the sample.
Patent Document 1 discloses that an amount of deformation of a pattern is detected by detecting a pattern edge of an inspection objective pattern with the help of the CD-SEM and by comparing it with a reference pattern.
Secondary electrons obtained by scanning the electron beam on the sample sometimes differ in generation intensity and in distribution of generated secondary electrons depending on the direction of scanning of the electron beam and on the direction of a pattern edge of the inspection objective pattern. Patent Document 1 and Patent Document 2 propose that in order to mitigate the above inconvenience, the electron beam is constantly scanned vertically to the direction of an edge of the pattern to be measured.
[Patent Document 1] JP-A-2004-163420
[Patent Document 2] JP-A-2005-116795